1. Field of the Invention
In general, the present invention relates to a storage system and a method of configuring the storage system. More particularly, the present invention relates to a storage system suitable for executing centralized management of management information of the storage system, which is capable of continuing its operation, that is, without halting the operation, when changing the storage system""s configuration comprising one storage controller or a plurality of storage controllers without regard to the configuration, and relates to a method of configuring the storage system.
2. Description of the Related Art
There are a variety of storage systems, from a large-scale storage system demanded by typically a data center of an enterprise to a small-scale storage system demanded by the general open market. In either case, performance and a storage capacity required of a small or large-scale storage system greatly vary in accordance with the application.
In order to solve a problem of scalability required of a storage system, there has been proposed a conventional method whereby a switch is provided between a host computer and a storage system so as to allow an additional storage system to be connected to the host computer by connecting the switch by using a transfer path used in connecting the storage systems to the host computer.
Also in order to solve a problem of scalability required of a storage system, there has been conceived another method whereby a plurality of components are connected to each other to form a multi-component storage system which appears to a host computer as a single storage system. In accordance with this method, data transfer paths and management-information transfer paths inside the multi-component storage system are typically connected to each other to integrate the components into a single storage system.
On the other hand, a micro program of a conventional storage system is written by assuming that the storage system serving as a control object both logically and physically has a structure of a single storage system. Thus, with a plurality of small-size storage systems connected to each other to form a single storage system, if all the storage systems are not regarded logically as a single storage system, it is necessary to revise the conventional micro program""s basic recognition of the storage system. In this case, a modification range involves the entire micro program and the scale of the modification becomes extremely large.
Thus, also when a plurality of components are connected to each other to form a single storage system, there is raised a demand to regard the structure of the connected components logically as the structure of the single storage system so that the micro program can be applied in a diversionary way.
If the structure of storage-system components is regarded logically as the structure of a single storage system, management information of the single storage system is information of integrity, that is, information that cannot be separated into portions of the storage-system components as is the case with the management information of the conventional storage system. For this reason, in order to store the management information, it is necessary to allocate a logically contiguous memory area as is the case with the conventional storage system.
As one of methods to allocate a memory area for storing management information, management-information memories distributed among storage-system components are used. If physically distributed management-information memories are to be managed logically as a management-information memory, however, a maintenance function becomes difficult to implement. This is because, in the conventional storage system, management information is stored in a physically single management-information memory.
Assume that a plurality of components or small-size storage systems are connected to each other to form a single storage system and, in the state in which the connected components appear as a single storage system, any arbitrary small-size storage system is removed. In this case, an area for storing a part of management area is also removed as well. Since the management information is information of integrity which cannot be separated into portions, the management information becomes unusable even if only a part thereof is lost. Thus, if any arbitrary small-size storage system is removed, it is necessary to halt the operation of the storage system.
By the way, members other than management-information memories each used for storing management information are also distributed among small-size storage systems. In implementation of a maintenance function for such members, the conventional maintenance method can be adopted in a diversionary way relatively with ease. This is because, the conventional storage system also has functions to partially block, maintain and recover configuration elements other than the management-information memories.
As described above, the conventional technology provides a method whereby a plurality of components or small-sized storage systems are connected to each other to form a single storage system. However, this method has the following problems.
In the method whereby a plurality of components or small-sized storage systems are connected to each other to form a single storage system, a technique to manage all the small-sized storage systems is not taken into consideration.
Thus, an attempt made to apply the micro program of the conventional storage system raises a problem that the scale to modify the micro program becomes extremely large and the diversionary application of the micro program becomes difficult.
In addition, the method whereby a plurality of components or small-sized storage systems are connected to each other to form a single storage system does not consider a technique to store the storage system""s management information of integrity that cannot be separated into portions of the small-size storage systems in management of the small-sized storage systems as a logically single storage system.
Thus, management information is stored in management-information memories employed in the physically distributed small-size storage systems, making the maintenance function difficult to implement. In addition, there is also raised a problem that, since the management information is also physically distributed, performance to make accesses to management information deteriorates as well.
Furthermore, in the conventional technology, a flexible technique of coping with changes in storage-system configuration is not taken into consideration either.
For example, when the storage-system configuration is changed from a configuration comprising a component of a storage system to a configuration comprising a plurality of components composing the storage system, making it necessary to transfer management information from one location to another, the operation of the storage system must be halted, raising a problem that a host is not capable of making an access to a disc storage in the mean time. This problem becomes serious in particular in a version-up process of a large-scale storage system which must be operated all the time.
It is thus an object of the present invention addressing the problems described above to provide a storage system that:
allows the configuration thereof to be changed with ease;
can be logically managed as a single storage system even if the single storage system is formed by connecting a plurality of components or small-sized storage systems to each other;
selects a storage location of management information in accordance with the configuration of the storage system so as to implement centralized management of management information without regard to the configuration of the storage system; and
does not allow performance to make accesses to management information to deteriorate.
It is another object of the present invention to provide a method of configuring a storage system that allows the configuration thereof to be changed without halting the operation of the storage system so as to allow a host to make an access to a disc storage while the configuration is being changed.
In order to achieve one of the objects described above, in accordance with the present invention""s aspect related to a storage system, there is provided a storage system allowing a host computer to make accesses to storages and comprising one or more storage controllers and the storages wherein:
each of the storage controllers includes:
a channel interface connected to the host computer;
an interface connected to the storages; and
a management-information memory for storing management information of the storage system;
if the storage system includes a plurality of the storage controllers, the management-information memories employed in the storage controllers are connected to each other by a management-information-memory switch having a switch-internal management-information memory module;
if the storage system includes only one storage controller, the management-information memory of the storage controller has a controller-internal management-information memory controller and a controller-internal management-information memory module;
if the storage system includes a plurality of the storage controllers, the management-information memories employed in the storage controllers each have the controller-internal management-information memory controller;
if the storage system includes only one storage controller, the controller-internal management-information memory controller makes an access to the controller-internal management-information memory module inside the storage controller; and
if the storage system includes a plurality of the storage controllers, the controller-internal management-information memory controllers make accesses to the switch-internal management-information memory module inside the management-information-memory switch.
To put it in more detail, if the storage system includes only one storage controller, management information is stored in the controller-internal management-information memory module inside the storage controller. If the storage system includes a plurality of the storage controllers, on the other hand, management information is stored in the switch-internal management-information memory module inside the management-information-memory switch.
In order to achieve the other object described above, in accordance with the present invention""s other aspect related to a method of configuring a storage system, there is provided a method of configuring a storage system allowing a host computer to make accesses to storages and comprising one or more storage controllers and the storages wherein:
each of the storage controllers includes:
a channel interface connected to the host computer;
an interface connected to the storages; and
a management-information memory for storing management information of the storage system;
if the storage system includes only one of the storage controllers, the management-information memory of the storage controller has a controller-internal management-information memory controller and a controller-internal management-information memory module; and
if the storage system includes a plurality of the storage controllers, the management-information memories employed in the storage controllers are connected to each other by a management-information-memory switch having a switch-internal management-information memory module and the management-information memories employed in the storage controllers each have the controller-internal management-information memory controller.
To put it in more detail, if the storage system includes only one of the storage controller, management information is stored in the controller-internal management-information memory module inside the storage controller. If the storage system includes a plurality of the storage controllers, on the other hand, management information is stored in the switch-internal management-information memory module inside the management-information-memory switch.
In order to achieve the other object described above, in accordance with the present invention""s other aspect related to the method of configuring a storage system wherein the management-information memories employed in each of the additional storage controllers and the management-information-memory switches consist of duplicated-management-information-storing systems, there is provided the method""s configuration for installing an additional one of the storage controllers whereby, when some of the storage controllers are newly installed in addition to only one of the storage controller already existing in the storage system:
the management-information-memory switches are newly added for connecting the management-information memories employed in the storage controllers to each other;
for each of the duplicated-management-information-storing systems, the management-information memory is connected to the management-information-memory switch;
to change stored locations of management information from the management-information memories of the storage controller already existing in said storage system to the management-information-memory switches, the duplicated-management-information-storing systems are sequentially subjected one system after another to a procedure comprising the steps of:
blocking one of the duplicated-management-information-storing systems;
copying management information of the unblocked one of the duplicated-management-information-storing systems from the management-information memory to the management-information-memory switch of the blocked duplicated-management-information-storing system; and
de-blocking the blocked duplicated-management-information-storing system; and
the storage system carries out processing of an access made by the host computer to the storages while the stored locations are being changed by using management information stored in an unblocked one of the duplicated-management-information-storing systems.
In order to achieve the other object described above, in accordance with the present invention""s other aspect related to the method of configuring a storage system wherein the management-information memories employed in each of the additional storage controllers and the management-information-memory switches consist of duplicated-management-information-storing systems, there is provided the method""s other configuration for removing any one of the storage controllers whereby, when some of the storage controllers are removed from the storage systems to leave only one of the storage controllers in the storage system with the management-information memories connected to the management-information-memory switch in all the duplicated-management-information-storing systems,
to change stored locations of management information from the management-information-memory switches to the management-information memories of the storage controller to leave alone in said storage system, the duplicated-management-information-storing systems are sequentially subjected one system after another to a procedure comprising the steps of:
blocking any one of the duplicated-management-information-storing systems;
copying management information of the unblocked one of the duplicated-management-information-storing systems from the management-information-memory switch to the management-information memory of the blocked duplicated-management-information-storing system; and
de-blocking the blocked duplicated-management-information-storing system, and
the storage system carries out processing of an access made by the host computer to the storages while the stored locations are being changed by using management information stored in an unblocked one of the duplicated-management-information-storing systems.
In order to achieve the other object described above, in accordance with the present invention""s other aspect related to the method of configuring a storage system, there is provided the method""s further configuration for installing an additional one of the storage controllers whereby, when some of the storage controllers are newly installed in addition to only one of the storage controllers already existing in the storage system:
said management-information-memory switch is newly added for connecting said management-information memories employed in said storage controllers to each other; and
to change stored locations of management information from the management-information memory employed in the storage controller already existing in said storage system to the management-information-memory switches, management information stored in the management-information memory is copied to the management-information-memory switch in a copy operation; and
the storage system carries out processing of an access made by the host computer to the storages while the stored locations are being changed by using management information stored in the management-information memory employed in the storage controllers each serving as a source of the copy operation.
In order to achieve the other object described above, in accordance with the present invention""s other aspect related to the method of configuring a storage system, there is provided the method""s still further configuration for removing any one of the storage controllers whereby, when some of the storage controllers are removed from the storage systems to leave only one of the storage controllers in the storage system with the management-information memories connected to the management-information-memory switch:
to change stored locations of management information from the management-information-memory switch to the management-information-memory of the storage controller to leave alone in said storage system, management information stored in the management-information-memory switch is copied to the management-information memories in a copy operation; and
the storage system carries out processing of an access made by the host computer to the storages while the stored locations are being changed by using management information stored in the management-information-memory switch serving as a source of the copy operation.